Trophic transfer of mercury in marine food chains from the offshore waters of Changshan Archipelago

Introduction Mercury (Hg) and its organic forms can accumulate in marine organisms, undergoing biomagnification as they transfer through food chains. However, the factors affecting such Hg biomagnification are not fully understood. Methods This study analyzed the biomagnification of total mercury (THg) and methylmercury (MeHg) in marine food chains represented by invertebrates and fish from the offshore waters of Changshan Archipelago, grouped into continuous trophic level (TL) ranges based on nitrogen stable isotopic analysis. Results Concentrations of THg and MeHg ranged from 4.8 ng/g to 115.4 ng/g and 1.8 ng/g to 47.3 ng/g in invertebrates, and from 3.7 ng/g to 102.1 ng/g and 0.5 ng/g to 67.6 ng/g in fish, with TL ranges for invertebrates and fish of 1.27–2.70 and 1.97–3.60, respectively. Hg concentration increased with increasing TLs in both fish and invertebrates. Combined with nitrogen stable isotopic analysis, trophic magnification factors (TMF) were 1.51 and 1.16 for THg and MeHg in fish, and 1.95 and 1.71 for THg and MeHg in invertebrates, respectively, indicating the biomagnification of THg and MeHg in the study area. Further analysis of Hg biomagnification showed higher TMF values of Hg in both invertebrate and fish groups with higher δ 13 C values, suggesting that food sources influenced Hg biomagnification in marine organisms. Discussion Food sources with lower δ 13 C values might reduce biomagnification efficiency of both THg and MeHg within marine fauna. These results aided understanding of Hg biomagnification in marine food chains and provided a reference for developing ways to harness Hg pollution.